[time-nuts] Mains Frequency

[Andy Talbot]

Streetlights now use radio control from a master, using, at least round
here, a GSM type of protocol on a dedicated frequency, so every individual
light can be set, at different brightness levels.   And they do do this -
at least on a street basis.  And they monitor every light.

I take the 50Hz in, pass it though a three stage RC filter then into the
TMR1 input of a PIC 16F628 which has a Schmitt input at thresholds of 30%
and 70% of the rails.  , ie 1.5 / 3.5V  so plenty of hysteresis.

Andy
www.g4jnt.com



On Fri, 12 Feb 2021 at 16:57, Adrian Godwin <artgodwin at gmail.com> wrote:

> I wouldn't be surprised to find that streetlight clocks use the same old
> Sangamo or Venner electromechanical timers that they've always used, and
> are far more of a problem to correct than domestic clocks.
>
> Andy, what equipment do you use to monitor the cycle count ?
>
>
> On Fri, Feb 12, 2021 at 2:55 PM Lux, Jim <jim at luxfamily.com> wrote:
>
> > On 2/12/21 3:12 AM, Andy Talbot wrote:
> > > I maintain a real time display of mains frequency, and the cumulative
> > > timing offset from real time.   It was last reset 10 days ago when we
> > had a
> > > brief power outage (HV fault a mile or so away).
> > >
> > > Since then, for the first few days the timing discrepancy kept within
> > > plus/minus perhaps 20 seconds.  But in the last couple of days is has
> > crept
> > > up and is now sitting at +48 seconds.   On average the frequency will
> > have
> > > been running about 0.013Hz high to give that.
> > >
> > > Given Nat. Grid still aim to average out to exactly 50Hz, does anyone
> > know
> > > if there is a time scale associated with that long-term average?
> >
> >
> > I would think they try to hold it over 1 day, so that mains driven
> > clocks don't run slow or fast.  That being said, I wonder how many
> > clocks are still being built using a synchronous motor drive? Given that
> > all the clocks on appliances in my kitchen have drifted apart, I'll bet
> > they use their internal microcontroller crystal as a reference.
> >
> >
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